1. Field of the Invention
The present invention relates to display technology, and more specifically, to a backlight module.
2. Description of the Prior Art
Given that a traditional thin-film transistor liquid crystal display (TFT-LCD) panel does not emit light, an external light source must be added for the panel to display. This kind of external light source is usually a backlight source or reflective light source. The light emitted from a backlight source is little influenced by changes of environmental factors, therefore most of the TFT-LCDs nowadays apply backlight source.
The backlight source of TFT-LCD has evolved from cold cathode fluorescent lamp (CCFL) to light-emitting diode (LED). Because LED has many advantages, including small size, quick reaction, long lifespan, not being fragile, high color gamut and multiple packaging bodies, it has become the mainstream in backlight source.
LED backlight can generally be divided into edge-lit LED and direct-lit LED. The edge-lit LED consumes lower energy and is thinner, but must be used with a light guide plate, rendering it heavier and of higher production cost. On the other hand, the direct-lit LED uses less light sources (with prism) and does not need a light guide plate, therefore the cost is lower, but it looks thicker as the lightbox is relatively higher.
The spectrum of light emitted by quantum dot (QD) fluorescent powder has a narrow full width at half maximum (FWHW), ranging from 20 a to 40 nm, so its color purity is extremely high, the highest among all existing fluorescent powders to realize color purity. However, because QD fluorescent powder is synthesized through chemical solution, it is difficult to distribute evenly along with silica gel. In addition, it is water-sensitive and oxygen-sensitive, and the light emitted from it can be seriously affected by thermal quenching. If it is directly packaged in the LED, it would have low luminance and reliability, and cannot be put into mass production. Currently, a viable solution to mass-produce QD fluorescent powder is remote fluorescent powder, the most noticeable one being 3M's quantum dot enhancement film (QDEF). The product has a layered structure and QD is packaged in optical films, which will be applied with other optical films. Another representative product is QD Vision's QD tube, which packages QD powder in a glass tube. When applied, the QD tube is put in front of the LED and fixed by supportive structures. However, presently the application of the QD film to ultra-large products is limited as QD films cannot be larger than 100 inch in width due to the size limit of entities. Meanwhile, the QD tube can only be applied to edge-lit LEDs as it is difficult to assemble bended glass tubes, which are extremely fragile. In addition, the size of the light guide plate, due to limits of current technology, cannot be larger than 98 inch. Given these various reasons, it is difficult to apply QD technology on ultra-large products with regular optical design approaches.